1. Field of the Invention
The present invention relates to a chip evacuation device and particularly relates to a chip evacuation device in which operation of a driving unit can freely be controlled depending on situations.
2. Description of the Related Art
In chip evacuation devices such as chip conveyors, commonly, an induction motor and an electromagnetic switch or an magnetic contactor are used as a driving source. Number of rotation of induction motors depends on power supply voltage and is therefore made constant except for occasions of start and stoppage of operation of the induction motors. Direction of rotation of induction motors is restricted to one direction in general.
Japanese Patent Application Laid-Open No. 2010-137931 discloses use of an inverter (in place of an electromagnetic switch or an magnetic contactor) as feed changing means that is capable of switching an induction motor into any of drive statuses, that is, forward rotation, stoppage, and reverse rotation by changing status of feed from a power source to the induction motor in a drive controller for a conveyor that controls the status of feed to the induction motor in the conveyor.
In a configuration in which an induction motor is controlled with use of an magnetic contactor or an electromagnetic switch, the number of rotation of the induction motor depends on a frequency of power supply and thus cannot be changed to an arbitrary number. Besides, it is impossible to make a change between forward rotation and reverse rotation unless a reversible magnetic contactor is used. Accordingly, there is a problem in that operation of a chip conveyor, that is, number of rotation of the driving source, cannot automatically be changed in accordance with status of production or deposition of chips in a machine tool.
In a prior art technique disclosed in Japanese Patent Application Laid-Open No. 2010-137931 described above, the induction motor can be operated at an arbitrary number of rotation including that for the reverse rotation, whereas the induction motor (and a driving unit of the chip evacuation device) cannot be moved to and stopped at an arbitrary position because any rotation detector is not used in the induction motor and because any means for receiving and processing signals from a rotation detector is not included in the induction motor.
In addition, it is impossible to check the direction of rotation of the induction motor because operation of the induction motor is not monitored. Therefore, the induction motor may be rotated in a direction different from an intended direction because of wiring errors in the induction motor or the like.